Identification of phosphatidate nonlamellar phases on liposomes by flow cytometry

This study is the first report that demonstrates nonlamellar arrangements, or lipidic particles, of phosphatidate inserted in the lipid bilayer of liposomes using polyclonal antibodies from mice and flow cytometry. Sera immunoreactivity was analyzed using liposomes that displayed smooth bilayers of phosphatidate particles, as shown by electron microscopy. This cytofluorimetric analysis showed that immune mice sera have a specific immunoreactivity with the phosphatide particles formed by Mn2+, which also cross-reacted with those formed by Ca2+ and with cardiolipin particles formed by Mn2+. In addition, these immune sera hardly reacted with smooth bilayered liposomes, independently of the lipid composition studied. Thus, this new methodology can be applied to demonstrate nonlamellar molecular arrangements in biological membranes.